1. Field of the Invention
The present invention relates to side members located on either side of the body of an automobile so as to extend in the longitudinal direction of the automobile.
2. Description of the Related Art
An automobile comprises a pair of side members in reinforcing members for the body of the vehicle, which are located individually on the left- and right-hand sides of the vehicle body. The side members extend rearward from the front of the vehicle body, passing under the interior of the vehicle. In the front part of the vehicle interior, the left- and right-hand side members are jointed to a cross member and a dash panel, which cross the vehicle body in its crosswise direction (see FIG. 1 of Jpn. UM Registration Publication No. 2522690, for example).
The side members include an upper panel and an under panel each. The upper panel is in the form of a flat plate and extends forward from a junction with the cross member. The under panel has a hat-shaped cross section that spreads upward. It extends forward from the junction with the cross section and extends rearward, passing under the vehicle interior along the dash panel.
The cross member has a hat-shaped cross section that spreads rearward and is jointed to that part of the dash panel which is located outside the vehicle interior. Junctions of the cross member with the side members project forward or toward the side members. Further, the opposite end portions of cross member, with respect to the direction of the vehicle width, are bent rearward. The side members and the cross member are spot-welded to one another on two surfaces, outside and inside wall surfaces with respect to the direction of the vehicle width.
The rigidity of the front part of the vehicle is enhanced by transmitting a load on the side members to the cross member through the junctions.
However, the side members and the cross member are jointed together at the junctions on the outside wall and the inside wall, and are neither on a top wall nor on a bottom wall (lower wall of the under panel). Therefore, a load of a head-on collision or lateral collision is concentrated on the joints on the outside and inside walls without being transmitted from the top and bottom walls to the cross member. Thus, the side members easily bend near their junctions with the cross member.
The upper panel (top wall) of each side member is discontinued in front of the dash panel. The inside and outside walls of the under panel of the side member are jointed to the cross member and the dash panel by means of flanges. While the vehicle is running, the side members may be twisted by a load that is transmitted from the front wheels. If the side members are not rigid, in this case, the load is concentrated on the flange portions that are jointed to the cross member and the dash panel, and a force acts to tear them off. Thus, the welded joints are easily deformed.
Junctions of the cross member to be inserted into the side members are formed by projecting the cross member by press molding. If the junctions project much, they require deep drawing, which is a hard work. Therefore, the height of projection of the junctions cannot be made greater than a certain value. Thus, it is hard to enhance the rigidity of the front part of the vehicle by increasing the strength of bond between the side members and the cross member.